The invention relates to an exposure control device for cameras having a combined diaphragm and sector shutter.
It is known that a camera which provides a programmed exposure control may utilize a so-called triangular opening scheme in which a combined diaphragm and sector shutter is opened gradually so that a triangular response of the exposure is produced with respect to time and the shutter is closed when a proper amount of exposure has been provided. With this scheme, the photometry of light from an object being photographed which changes with time is achieved through a sub-diaphragm which opens in mechanically interlocked relationship with the sector shutter. However, it is found that the opening of the sub-diaphragm is lagging with respect to the opening of the sector shutter in the camera of the type described, and there has been a need to compensate for such lagging by the provision of some means (see Japanese Laid-Open Patent Application No. 32,082/1980). Obviously, the sector shutter remains closed before a release operation takes place, thus preventing the photometry. This accompanies a disadvantage that a warning concerning low brightness cannot be given before the release operation.